Field of the Invention
The embodiments of the invention relate to an organic light emitting diode (OLED) and more particularly to an organic compound being capable of reducing a driving voltage and being adequate to a simple structure OLED and an OLED including the organic compound.
Discussion of the Related Art
Developments in information have led to developments in flat panel display devices as an image displaying device. The flat panel display device includes a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED) and an organic light emitting diode device (OLED), and the flat panel display device meeting the demand for thinness, light-weight and low power consumption are introduced.
Among the flat panel display devices, the OLED has various advantages as compared to the LCD, the PDP and the FED. A flexible substrate, for example, a plastic substrate, can be used as a base substrate for the OLED, and the OLED has excellent characteristics of driving voltage and power consumption.
FIG. 1 is a cross-sectional view of a related art OLED.
As shown in FIG. 1, the OLED 20 is formed on a substrate 10 and includes a first electrode 21 as an anode, a second electrode 27 as a cathode, and an organic emitting layer therebetween. To increase an emission efficiency, the organic emitting layer includes a hole injection layer (HIL) 22, a hole transporting layer (HTL) 23, an emitting material layer (EML) 24 and an electron transporting layer (ETL) 25 and an electron injection layer (EIL) 26.
Holes are provided from the first electrode 21 into the EML 24 through the HIL 22 and the HTL 23, and electrons are provided from the second electrode 27 into the EML 24 through the EIL 26 and the ETL 25.
The holes and the electrons are combined to form excitons, and the excitons are transformed from an excited state to a ground state. As a result, the OLED 20 emits light.
As mentioned above, the OLED requires a plurality of layers to increase the emission efficiency. To prevent the quenching problem of the excitons, the OLED further requires an electron blocking layer and a hole blocking layer. As a result, the production costs of the OLED are increased, and the production yield of the OLED is decreased.
In addition, there are still barriers between adjacent layers. Particularly, there is a hole injection barrier between the HIL 22 and the HTL 23 and/or between the HTL 23 and the ML 24, and the velocity of the electron injection and the electron transporting is larger than that of the hole injection and the hole transporting. Accordingly, the combination of the holes and the electrons is generated in a boundary region between the EML 24 and the HTL 23—not a center region of the EML 24—such that the emission efficiency is decreased and the driving voltage is increased.
To resolve the above problems, the simple structure OLED is required. In addition, a balance of the velocity of the holes and the electrons is required to form the excitons in the center region of the EML.